Tools of Characterization
The name of the villain is also the name of the novel, so it's something we're meant to think about a bit. "Dracula" comes from the Romanian word "Dracul," which means "dragon" or "devil." Appropriate, don't you think? (See "What's Up With the Title?" for more on the vampire's name.)
But other names in Dracula carry symbolic weight as well. Dracula's first victim in Great Britain, Lucy Westenra, represents all the purity and innocence that the men want to protect. And her name reflects that: Lucy comes from the Latin word for "light," so "Lucy Westenra" could mean "Light of the West." Since Dracula's invading from the east, Lucy's name could suggest her role as an exemplary "Western" woman.
Speech and Dialogue
You can tell the difference between Mina's character and Lucy's just from looking at the first lines of two of their letters to each other. Mina, we know, is sensible and intelligent, while Lucy is more vivacious and bubbly. Check out the first line of one of Mina's letters to Lucy:
My dearest Lucy,—
Forgive my long delay in writing, but I have been simply overwhelmed with work. (5.1)
Compare that formal, sensible-sounding tone with Lucy's later letter to Mina:
My dearest Mina,—
Thanks, and thanks, and thanks again for your sweet letter! (5.6)
Lucy's reply makes her sound like what she is: a bubbly schoolgirl writing to an old friend.
Profession is important in Dracula—all the major professions are represented. Dr. Seward is a medical doctor; Dr. Van Helsing is a medical doctor and a professor/scholar; and Jonathan Harker is a lawyer.
All three of those men act as you'd expect stereotypical members of their professions to act: Jonathan is bookish, intelligent, and quiet. Dr. Seward is always making observations about how pale people look. And Dr. Van Helsing seems to know everything about everything... no wonder characters sometimes refer to him simply as "the Professor."